What did McGill do to Leonard Cohen's brain?

 Leonard Cohen was 17 when he agreed to participate in psychological experiments at McGill in 1951, conducted by Donald Hebb, according to research by author Ann Diamond.  
 Unlike others, Cohen is said to have enjoyed the sensory deprivation experience and participated frequently and that's what he's seen here doing.
 Removing stimulation can have "serious effects on the physiology of the brain," as Hebb conceded in an interview 20 years later. Hundreds signed on to the experiment, which paid an impressive $20 a day, a good sum at the time. Only 72 of them stayed long enough to provide useful information. And of those 72, only six did it for the full six days. We don't know if Cohen was one of those six, but based on his apparent subsequent comments, it seems quite likely that he spent considerable time doing it. .
Leonard's subsequent bout with profound depression is well documented, as his is quest for truth through spirituality and of course his fantastic success in music and poetry.
  Living in the early 50s, without TV, internet, must have given people some solid training in sensory deprivation but the experiments were undoubtedly dangerous and it would be interesting to get a follow up on the subjects and the long term effects they had.
  Diamond, who idolized Cohen as a teen, later became his neighbour and had a turbulent relationship with him and his entourage, as discussed in this brilliant post from her site. She muses whether Cohen was part of a lifelong mind-control MKULTRA experiment conducted at McGill later famously under the guise of Dr. Ewan Cameron.